Electron oscillation generator and phase modulator



1940- I a. 1.. USSELMAN 2.210.015

ELECTRON OSCILLA'IION GENERATOR AND PHASE llODULATdR Filed lay 29. 5Sheets-Sheet 1 OUTPUT SOURCE L5 INVENTOR aim/551,144

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ELECTRON OSOILLATION GENERATOR AND PHASE MODULATOR Filed lay 29. 1937 5Sfieets-Sheet 5 'swauaL saunas INVENTOR 6. L. USSELMAN w'u-bx/ ATTORNEY30 equivalent means.

Patented Aug. 6, 1940 UNITED STATES PATENT "OFFICE ELECTRON OSGILLATIONGENERATOR AND PHASE MODULATOR George Lindley Usselman, Port Jefferson,N. Y assignor to Radio Corporation of America, a

corporation of Delaware Application May 29, 1931, Serial No. 145, A

18 Claims.

electrodes which form part of a tube structure,

' modulating the electron stream in accordance with the producedoscillations, and impressing on said oscillations and said priormodulation effect,

phase variations in accordance with signals, and

thereby producing high frequency oscillatory energy in the anode circuitof substantially constant' mean frequency and of a phase characteristicof the modulations impressed at signal frequency on the oscillations.

A feature of the invention is the combined oscillation generator andphase modulator of the electron coupled type. The circuit may beneutralized or reaction may be prevented by the use of a groundedelectrode intermediate the electron 5 generating electrodes and theoutput electrodes.

The oscillation generators of my novel invention in several oftheirmo'dified forms, have no resonant electrical circuit associateddirectly with the oscillating circuit except a crystal or This circuitbeing electronically coupled by the electron stream only in the tube tothe anode is unaffected by changes in impedance which are produced inthe anode circuit due to the, variations in phase in the energy 3produced therein such as those which might be produced by changes in-tuning or changes in load. Thus, stable operation of high efllciency isobtained. Stabilization and efiiciency is further enhanced by utilizingshielding means between 40 the crystal electrodes and between theelectron generator electrodes and the output electrodes and byneutralizing the oscillation generation circuits. In other modifiedforms of my invention the output circuit is also substantially un- 5tuned in which case additional stabilization is obtained.

In all of the modifications wherein the output circuit is tuned the samemay be tuned to the frequency of the frequency stabilizing element inpiezo-electric type. The anode electrodes are connected in push-pullrelation with an output circuit which electrodes and circuit may beisolated with respect to the generating circuits by shielding electrodeswhich may be grounded for 5 the produced oscillations or by neutralizingmeans. In corresponding leads to like controlling v electrodes I insertphase displacing reactances which produce relative phase displacement ofthe oscillations generated. erThese displacing re- 10 actances' may alsobe disposed in the leads to the output circuit from the anode. Bymodulating the impedances of the tubes in phase opposition at signalfrequency the two tubes supply varying amounts of high frequency energyto the output 15 circuit so that the resultant energy in the outputcircuit has a phase determined to a large extent by the phase of theenergy supplied by that tube supplying the most energy at the particularin-' stance.

The modulating potentials may be applied at any of the severalcontrolling electrodes including the cathodes and the anodes of thetubes.

Due to the symmetrical arrangement the oscillator circuit has excellentfrequency stabilization together with high energy output. The entirehigh frequency circuit is well balanced as is the modulating circuit, sothat phase modulation as applied to the circuit is well balanced therebyproducing a good output with small distortion so and little amplitudemodulation.

While, for purposes of illustration I have shown my invention as appliedto generators and modulators of the push-pull type, it will beunderstood that the same is operative with a single tubeor substantiallyone-half of the circuits illustrated. In the latter case some amplitudemodulation may-be inherently accomplished during the phase modulationprocess but this can be removed by expedients well known in the art,such as amplitude limiting, etc.

In describing my invention reference will be made to the drawingsthroughout which, insofar as possible, like reference charactersindicate like parts and in which Figures 1 to 8 inclusive show variousmodifications of my novel oscillation generator and/or means for phasemodulating oscillations generated by the same.

In Figure 1 the pair of electron tubes V1 Vzare connected substantiallyin push-pull relation at their outputs, which are electronically coupledto the crystal stabilized oscillation generating circuits connected withthe controlling electrodes. The phase shifting reactances C and Lcrossconnect electrodes of the crystal with the conbe made to Figure 3of the drawings which show applied to the controlling grids. Shieldgrids are provided to further isolate the output circuit and theoscillation generating circuits;

Figure 2 is similar in many respects to Figure 1. In Figure 2, however,the phase shifting reactances C and L are connected somewhat differentlywhile the modulating potentials are applied to the screening electrodesand neutralizing cir cuits are provided. I

In Figure 3 the oscillation generator circuits only are shown andcross-neutralizing between the screeningelectrodes which form the anodesof push-pull oscillation generator and the controlling.electrodes isused. Any of the electrodes may be subjected to modulating potentials.Figure 3 shows this new' crystal oscillator circuit without means formodulation. This circuit is the basis for the circuit in whichmodulating means are provided.

In Figure 4, which is in some respects quite similar to the arrangementof Figure 1, modulation is applied to different grid electrodes, whichalso serve as the anodes of the oscillation generator circuits. Hereagain, cross-neutralization is used but the connections between thecrystal and tube electrodes are uncrossed which is important as will beseen later since the mode of oscillation is different from that in thepreceding figures.

The circuit in Figure 5 includes features of the circuit in Figures 1and 3 and in addition utilizes from the prior flguresin that tubes ofdifferent types having additional electrodes areutilized. Both Figure 6and Figure-'7 like Figure 4, have uncrossed connections to the crystalelectrodes.

Figure 8 is a modification of the arrangement of Figure 7.

The novel method of and means for producing oscillatory energy will nowbe described and in. describing said method and means reference willbeen designated by reference numbers I, 2, and 3,

respectively. The tubes may also each include a ground shield not shownbetween the pairs of electrodes on each end of the crystal. The

heater electrodes H1 H2 are connected with any source of potential suchas for example, shown at Band to ground as shown. The cathode electrodesK1 K2 are connected to the respective heater electrodes and to ground.The piezoelectric crystal X has two pairs of electrodes E1 E:

and E3 E1. E1 E2 are connected as shown to grids I in the two tubes V1and V2. These may, in practice, be the controlling grids. ElectrodesEz'and E1 are cross-connected as shown to #2 grids in tubes V2 and V1.Grids I of tubes V1 and V11 are also connected together as shown byappropriate resistances R1 R: and the electrical center of these 7resistances is connected to ground by an addisource by a by-passcondenser C4.

wave energy directly to any output circuit or to k R 2,210,016 trollinggrids. The modulating potentials are A tional resistance R3 shunted by aby-pass condenser Cs. Grids 2 of tubes V1 and V: are connected together.by resistances R1 and R5, the electrical center on R1 R5 beingconnectedto a point of appropriate positive potential on source, 3relative to the cathodes as shown. The potential source included in thislatter circuit is shunted by by-passing condenser. C1. The additionalelectrodes 3 are connected together by resistances R6 R7, the junctionpoints of the said resistances being connected to a point of positivepotential relative to the cathodes. Radio frequency potentials asgenerated are shunted around these resistances and the energizing sourceby condensers C1 C2 connected as shown. The anodes A1 A: are connectedtogether by a tuned circuit C; L1, a point on the inductance L1 of whichis connected to a point of positive potential relative to the cathodes.High frequency potentials appearing in this circuit are shunted aroundthe potential L1 may supply an output circuit coupled thereto as shownat In.

In some cases and in particular where high frequency oscillations are tobe generated in the circuits connected between the cathodes andthecontrolling electrodes I and 2, it may be desirable .to neutralizethe capacity between grids I and 2.

This may be done as shown'by connecting grid I of V to grid 2 of V2through neutralizing condenser N1 and by connecting grid I of V3 to grid2 of V1 through neutralizing condenser N2. These neutralizing condensersN1 and N2 neutralize the effect of capacity feedback between grids 2 andgrids I in the crystal oscillator circuit.

It may be stated .here that Figure 3 maybe modified by connecting gridsI and 2 in;each tube uncrossed to the crystal electrodes.- In thisbasethe neutralizing connections would have to -be crossed. Crossed anduncrossed grid to crystal connections produce different modes ofoscillation.

The oscillations generated in a manner described more in detailhereinafter may be modulated in phase. by providing means incorresponding circuits either in the oscillation generating circuits orthe output circuits for producing relative phase shift in the voltagesreaching corresponding electrodes or leaving corresponding electrodesand then varying in phase opposition the tube impedances. The tubeimpedances may be varied in phase opposition by applying modulatingpotentials to any of the electrodes therein in phase displaced relation.When the cathodes are modulated in phase displaced relation means mustof course be provided for raising the same above ground alternatingcurrentpotential.

In Figure 1 phase modulation is accomplished by connecting a-modulatingpotential source 0 in phase opposition to points on resistances R1 andR2 to control in phase opposition the potentials on electrodes I oftubes V1 and V2. In a particular application this modulating circuit mayinclude a transformer T having its primary winding connected to themodulating potential source and a secondary winding having its terminalsconnected to points on R1 and R: and its midpoint connected to theterminal of R3 and to a point intermediate two coupling condensers IIIand I2 separating biasing and modulating re sistors R1 and R2. The phaseshifting reactances designated by L and C are cross-connected betweenthe electrodes E1 and E2 of crystal X and controlling grids I of tubesV2 and V1 respectively in Figure 1.

L are directly (uncrossed) connected between electrodes E1 and E2 andcontrolling grids I of tubes Vl' and V2 respectively. In Figure 1 noneutralizing circuits are used. The electrodes 3 are at ground radiofrequency potential and shield the output electrodes and circuits fromthe generation and modulation circuits. In Figure 2 the electrodes I and2 of tubes V1 and V2 are connected to the grids 2 and I of V2 as inFigure 3. The electrodes E3 E4 and grids 2 are cross-connected as inFigure 3. The circuits of Figures 1 and 2 are otherwise suflicientlysimilar to the cir cuit of Figure 3, described in detail hereinbefore torender undesirable further description thereof.

The phase shifting reactances L and C need i not necessarily beconnected in the leads to electrodes I of tubes V1 and V since obviouslythey may be removed therefrom and inserted in the leads to electrodes 2of tubes V1 and V2 or in the leads connected between the anodes of V1and V2 and the tank circuit L1 'Cs.

The operation of the crystal controlled .osci1-- lator as illustrated inFigures 1, 2, and 3 and in particular in Figure 3 is as follows. Thegrids I and 2 of tubes V1 and V2 are cross-connected or coupled throughthe crystal X so that the oscillating potentials on grids I and 2 ineach tube will oppose in phase sufficiently to maintain oscillations inthe tubes and circuits when the crystal oscillates. These oscillationsin the crystal are of the well known thickness vibrations, e. g., of afrequency determined by the thickness of the crystal. Electrical energyoscillations are fed to the crystal from #2 grids which keep thecrystals oscillating mechanically. These mechanical oscillations areconverted to electrical potential osgillations and then delivered to #Igrid of each tu e. out of phase relation between grids #I and #2 in eachtube which will produce oscillations.

The amplified oscillations in the tubes are fed to grids #2 and theprocess is repeated or accumulativeso that sustained oscillations ofsubstantially constant frequency are produced in the tubes and circuits.

Positive potential is supplied to #2 grids through resistors R4 and R5from the source B. Negative bias potential is obtained through currentrectification in the circuits to the #I grids which produce biasingpotentials in resistances R3, R1, and R2, the resistance R3 beingby-passed by a radio frequency by-pass condenser C6.

The resistors R1, R2, R4, R5 supply grid and anode circuit impedance,without which oscillations would be of low amplitude resulting ininefllcient and poor operation.

As to the oscillator generator circuits, grids #3 of each tube beinggrounded for high frequency wave energy by condensers C1 and C2 whichserve as s eens or shields to prevent capacity reaction between theprimary anodes A1 and A: and the oscillation generating circuits of thetube including the grid-like electrodes 2 which serve as anodes for theoscillation generating circuits.

In the modification shown in Figures 1, 2, and 3 the only oscillatingmeans in the circuits producing the oscillations is the crystal X 50that,

due'to the natural stabilization of the crystal,-

The resulting oscillations are more than out hereinbefore.

amplitude for reasons pointed The anode circuit obtains its energy orpotentials through electron stream .coupling solely, which stream passesthrough the screening electrodes 3 of each tube. Thus, the anode tuned.circuit L1 C5 may be adjusted to resonance by means of variablecondenser C5 and such adjustment of -the anode circuit or externalchanges of any other impedance which is produced therein due to loadoscillation, is of minimum effect on the oscillating generating circuitsand consequently on the frequency produced by said circuits. With zerotemperature coefficient crystals this entire circuit becomes extremelystable in frequency since changes in the load circuit have substantiallyno effect on the crystal oscillations.

The anode circuit L1 C5 may be tuned to select either the fundamentalcrystal oscillator frequency or any odd harmonic thereof. Even harmoniescould only be produced by connecting both anodes tothe same end of theanode circuit L1 Cs. I

In describing the manner lations produced are modulated in phase,reference will first be made to Figure 1 of the drawings. InductanceLconnected between crystal electrode E2 andgrid I of tube V1 togetherwith resistor R1 connected between grid I of tube V1 and ground throughby-passing condenser I0 produce a lagging phase in the excitationdelivered from the crystal to the grid I of tube V1. Ina similar mannercapacity C and -re- .sistor R2 connected between grid I of tube V11 andground through by-passing condenser I2,

produces a leading phase in the excitation voltage delivered to grid Iof tube V2 by crystal X. In other words, there is produced a fixedalthough adjustable phase angle or difference between the excitationvoltage delivered to the #I grids of tubes V1 and V2. This causes eachtube to deliver or repeat or amplify these electrical oscillations onimpulses with the same phase shift or difference. With proper electrodebias and equal or zero modulating potentials on the #I grids each tubesupplies equal amounts of energy to the tank circuit L1 C5 (which mightbe zero or any value of energy within a reasonable range) so that theresultant energy in L1 C5 takes up a mean fixed phase position. In thepresence of exact symmetry this resultant mean fixed phase relationshould be in synchronism as to phase and frequency with the oscillationsgenerated in the generator electrodes and circuits or harmonics thereof.As to the oscillation gen erator circuits per se, because of the inertiaor fiy-wheel effect of the crystal it tends to operate at asubstantially constant frequency with a phase angle substantially theaverage of that delivered by the tubes V1 and V2. However, in thepresence of modulating potentials the potentials on the #I grid of tubesV1 and V2 are varied in phase opposition at signal frequency. Thiscauses the tube which has the more favorable grid potential to delivermore power'to the tank circuit L1 C5 and thereby cause the phase of theenergy in said tank circuit to approach the phase of the energydelivered by the said tube. Consequently as each tube has its impedancevaried or modulated in phase opposition, the phase of the output energyin circuit L1 C5 is caused to swing back and forth in accordance withthe modulating potentials between limits determined by the initiallimiting phase shift in}- parted to the excitation voltages by phaseshifting reactances L and C.

The frequency of the phase swing is determined by the signal frequencyand the degree or amount of phase swing varies in accordance with thesignal intensity or amplitude.

In Figure 2 the modulating potentials are applied to the screeningelectrodes 3 to modulate in a manner similar to that describedhereinbefore in connection with Figure l the ability of the tubes todeliver current to the tank circuit L1 Ca. These modulating potentialsbeing in phase opposition cause tubes V1 and V2 to supplyinstantaneously, various amounts of current to the tank circuit so thatthe resultant current therein takes up a phase position correspondingmore closely to the phase position of that tub'e supplying the mostenergy which in turn corresponds to the application at' signal frequencyof the more favorable controlling potential to the tube electrode.

In a preferred embodiment as illustrated in Figure-4, the modulatingpotentials are supplied or applied in phase opposition to the #2 gridswhich also serve as the anodes of the oscillation generator circuits oftubes V1 and V2. The operation of this modification will be readilyunder stood from the description of the phase modu lators illustrated inFigures 1 and 2 and need not be repeated at this point. Applicant wishesto note, however, that in the arrangement of Figure .4 as compared to,say, Figures 1, 2, and 3, the

grids I and 2' in Figure 4 as to their connections with the crystal areun-crossed. That is to say,

rids #I and #2 of each tube are connected to crystal electrodes on thesameside of the crystal. Theoretically at least, the oscillator, ofFigure 4 is more correct and is more flexible than the oscillator ofFigures 1, 2, and 3. In the circuit of Figure 4 cross-neutralization isutilized as in Figures 2 and 3. In Figure 4, however, a grounded shieldS is inserted between the electrodes E1 E2 and E1 Eran'd astri-dethe-crystal as shown. The shield S does not touch the crystal but does Icome between the pairs of electrodes on the crystal to thereby preventelectrostatic coupling between the pair of electrodes on one end of thecrystal and the pair of electrodes on-the other end of the crystal.Thus, the only coupling'between the #I grids of the tubes V1 and V2 andthe #2 grids of the tubes VI. and V2 which act as the crystaloscillation circuit anodes is through the mechanical coupling of thecrystal because the neutralizing condensers N1 N2 neutralize thecapacity of the tube elements. This circuit was found to oscillatereadily and produce sustained oscillations of substantially --constantamplitude and frequency and to have other features such as to make it amost desirable modification. The circuit has greater frequencystabilization and it also operates or functions in accordance with areadily understandable theory. The phase reversal (approximately 180)between the #I controlling electrodes and the #2 grid-like anodes occursin the crystal X. Assume #2 grid in tube V1 positive and #2 grid in tubeV2 negative and that the current is flowing through the crystal X fromelectrode E to electrode E4. Then, itis known that the current flow inthe crystal X between electrodes E1 and E2 will be in the same directionthat is a fixed or' generated current. Consequently, the voltage onelectrodes E1 and E2 is a counter-voltage which is the reverse of thevoltage on the electrodes E3 and E4. Therefore the voltage of controlgrids I in tubes V1 and V2 is in phase opposition to the voltages on theanbde-like grids I in tubes V1 and V: which additional feature not foundin the prior figure.

In Figure 5 the generated oscillations are stabilized as to frequency bymeans of a. line of low power factor or low loss or a line in which theenergy displaced per cycle of alternating current is extremely low ascompared to the circulating current. This line comprises elements A andB which replace the usual crystal. The line A,'B' is of the double endedor push-pull type although any suitable type may be, used, such as forexample, any line following the teaching of P. S. Carter and C. W.Hansell in their publication Frequency control by low power factor linecircuits appearing in the April 1936 I. R. E. at page 597. The smallimpedance link Z is provided in order not to destroy the couplingbetween the two halves A and B of the line. The #I grids of tubes V1 andV1: are connected as shown to spaced points on the inner member B whilethe electrodes 2 of tubes V1 and V: are cross connected to spaced pointson the inner member Bv of the line. The line is preferably of a halfwavelength or shorter and when energized and connected as shown with thetube electrodes feeds potentials in phase opposition to. the #I gridswhich are amplified in the tube and fed from the #2 grids back to theline. The connections are such that the potentials on the grids I and 2in each tube are in phase opposition which is again the ideal conditionfor the production of oscillations.- from the line to the tubes and fromthe tubes to the line so that a fiy-wheel oraccumulative effect isproduced and oscillations are produced in the tubes, circuits and lineof a frequency determined by the dimensions of the line A, B. Modulationis accomplished as in Figure 1.

In Figure 6, which is in many respects similar to the arrangement shownin Figure 4, the tuned output circuit has been replaced by a resistivecircuit including resistors Ra Ra. Thus, in this arrangement we have notuned or resonant circuits either in the output of the tube or in theoscillation generator portion of the system other than the crystal.Obviously improved operation is obtained by this circuit as far asfrequency stabilization and waves of constant amplitude linearly phasemodulated is concerned. This circuit will operate only on thefundamental frequency of the crystal since there are no tuned circuitsto select harmonics.

In the arrangement of Figure 7, which in some respects is somewhat likeFigures 4 and 6, I have utilized at V1 and V2 tubes of the RCA 6L7 typehaving five grids. This arrangement is in other respects similar to thearrangement discussed in connection with the prior figure. Theadditional grids 5 may be connected as shown to ground or if desired maybe maintained at a potential slightly above or below ground potential.Here again the output circuit electrades are connected with impedancesRa Ra which may be resistances or reactances or may be replaced by atuned circuit which in turn may be tuned either to the crystal frequencyor to a harmonic of the frequency of the crystal.

Potentials are fed Y The oscillation generator electrodes are connectedwith the crystals as in Figures 4 and 6.

I odes and the oscillation generator circuit which feeds energy to theanodes by way of the electron stream due to the additional electrodesand to the eifect of the screening electrodes 4. Neutralizing condensersare unnecessary in this arrangement and, as will be seen, have beenomitted. Figure 7 may use any of the features used in the precedingfigures. For instance, we may use aresonant line in Figure 7 instead ofthe crystal, as shown in Figure 5.

It is important to note here that by suitable arrangements modulatingpotentials from S1 and T may be applied to #5 grids instead of the othergrids as it has been done in the preceding figures. This modification isshown in Figure 8. By introducing the modulation on grids 5 no reactionwhatever will be induced in the crystal oscillator circuits from themodulating potentials.

This is important since it would give a very practical and stablecircuit. In this case grids 5 would be by-passed to cathode by smallconden- .sers and the grids 5 would also be connect d in phaseopposition to transformer T. These grids could be supplied with anydesirable bias potential'from zero to any positive or negative valuewhich is practical.

Iclaim: 1. A phase modulation system comprising in combination, anelectron discharge tube having a plurality of electrodes some of whichare connected in oscillation generating circuits and an-' other of whichis connected in an output circuit coupled to said oscillation generatingcircuits substantially by the electron stream of said tube only, phaseshifting means in-'one of said circuits, additional means for separatingsaid gencuit coupled to said oscillation generating circuits by theelectron stream of said tube only, frequency stabilizing means in theform of .a resonant low loss line connected with. said oscillationgenerating circuits,a source of modulating potentials and means formodulating'the phase of the oscillations generated in accordance withsaid modulating potentials.

3. In a signalling system in combination, an

electron discharge device having a cathode, a plurality of auxiliaryelectrodes, and an anode, circuit means connected with at least two ofsaid auxiliary electrodes and said cathode for producing oscillations insaid device of substantially constant amplitude and frequency, anaperiodic output circuit connected with the anode of said device andcoupled to said oscillation generating electrodes and circuits by way ofthe electron stream only of the device, and means for modulating thephase of the produced oscillations comprising a phase shifting reactancein said circuit means and a source of modulating potentials coupled toelectrodes in said device for modulating the impedance thereof andconsequently the phase of the oscillations produced at signal frequency.

4. In a signalling system in combination, a-

plurality of electron discharge devices each having a cathode, aplurality of auxiliary electrodes, and an anode, circuits connected withat least two of said auxiliary electrodes and said cathode in each ofsaid devices for producing oscillations in said devices and circuits,phase shifting reactance of different character in correspondingportions of said circuits, an output circuit connected with the anodesof said devices, said output circuit being coupled to said oscillationgen erating electrodes and circuits substantially by way of the electronstreams only of the devices, means for shielding said output circuitfrom said auxiliary electrodes and means except for said electron streamcoupling, and means connected with an electrode ineach of said devicescontrolling the gain of said devices in opposition at signal frequencyfor modulating thepscillations produced at signal frequency.

5. In a signalling'system in combination, a plurality of electrondischarge devices each having a cathode, a plurality of controllingelectrodes, and an anode, circuits connected with at least twocontrolling electrodes and the cathode of each device for producingoscillations in said a phase displacement between the oscillationssupplied by said devices to said output circuit, and means connectedwith an electrode in each of said devices controlling the operativenessof said devices at signal frequency for modulating.

the phase of the oscillations produced at signal frequency. I

6.A phase modulated wave signalling system comprising in combination, asource of modulating potentials, an electron discharge device comprisingoscillation generator electrodes and an output electrode, circuitsinterconnecting said oscillation generator electrodes for the productionof oscillations, an output circuit connected with said output electrodeand coupled to said generator electrodes and circuits substantially bythe electron stream only of said electron discharge system, and means insaid circuits connected with=the electrodes of said discharge device formodulating the phase of the oscillations generated.

7. A phase modulated wave signalling system comprising in combination, asource of modulating potentials, an electron discharge device an outputelectrode, circuits interconnecting said oscillation generatorelectrodes forthe production of oscillations, an output circuitconnected with said output electrode and coupled to the comprisingoscillation generator electrodes and generator electrodes andinterconnecting circuits substantially by the electron stream only ofsaid electron discharge device, means for shielding said generatorelectrodes from said output electrodes, and means in said circuitsconnected.

with the electrodes of said device for modulating the phase of theoscillations generated.

8. In a system for producing oscillatory energy of substantiallyconstant frequency-and modulating the phase of the said energy inaccordance with signalling potentials, a pair of electrondischarge'tubes each having a cathode, a plurality of controllingelectrodes, and an anode rality of terminals, circuits inter-connectinga pair of controlling electrodes in each of said tubes and terminals ofsaid crystal, means for energizing said electrodes whereby oscillationsare produced in said tubes and circuits, phase shifting reactancesconnected corresponding controlling electrodes. in each of said tubes toproduce a of constant frequency and modulating the. phase modulatingpotentials and means coupling said source of modulating potentials inphase opposition to like electrodes in said tubes.

9. In a system for producing oscillatory energy of the said energy inaccordance with signalling potentials, a pair ofelectron-discharge'tubes each having a cathode, a plurality ofcontrolling electrodes, and an anode electrode, a piezo-eleotric crystalhaving a pluralityof terminals, circuits inter-connecting a pair. ofcontrolling electrodes in each of said tubes and terminals of saidcrystal, means for energizing said electrodes whereby oscillations areproduced in said tubes and circuits, phase shifting reactances connectedwith corresponding controlling electrodes in each of said tubes toproduce a relative phase displacement of the oscillations produced byeach tube, a nonreactive circuit connected with the anodes of saidtubeaa source of modulating potentials and means coupling saidsource ofmodulating potentials in phase, oppositionto like electrodes in saidtubes. i

10. A system as recited in claim 8 wherein said output circuit is tunedto a harmonic of the natural period of said crystal.

11. In a system. for producing oscillatory energy of constant frequencyand modulating the phase of the said energy in accordance withsignalling potentials, a pair of electron discharge tubes each having acathode, a plurality of controlling electrodes, and an anode electrode,a resonant low lossline, circuits inter-connecting a pair of controllingelectrodes in eachof said tubes and spaced points on saidline, meansforenergizing said electrodes whereby oscillations are produced in saidmeans, line, circuits, and tubes, phase shifting reactances connectedwith corresponding controlling electrodes in each of said tubes toproduce a relative phase displacement of the oscillations produced ineach tube,

an output circuit connected with the anodes of said line is the onlyresonant reactance in all of said circuits.

13. In a system for producing oscillatory en ergy of constant frequencyand modulating the phase of said energy in accordance with signals, apair of electron discharge tubes each having a controlling electrode, agrid-like anode electrode, a shielding electrode, and an anodeelectrode, a

piezo-electric crystal having at least two pairs' of electrodes, meansincluding phase'displacing reactances of different character connectingthe electrodes of one of said pairs'of crystals electrodes tocorresponding grid-likeelectrodes in said tubes, means connecting theelectrodes of another pair of electrodesof said crystal to dif- L ferentcorresponding electrodes in said tubes, '9. source of modulatingpotentials, means for ap- 2,210,015 electrode, a piezo-electric crystalhaving a plu-- plying modulating potentials in phase opposition. fromsaid source to corresponding electrodes in said tubes, a' circuitconnecting the anodes of said tubes in push-pull relation, and a circuitconnecting said shielding electrodes to the cathodes of said tubes.

14. A system as recited in claim 13 whereinthe crystal electrodes ofeach of said pairs of crystal electrodes are on opposite sides of saidcrystal and the connections between the electrodes of said crystal andthe electrodes of said tubes are direct.

15. In a system for producing oscillatory energy of constant frequency'and modulating the phase of said energy in accordance with signals, apair of electron discharge devices each having a controlling electrode,a grid-like anode electrode,- an additional grid-like electrode and an'anode electrode adjacent said additional electrode, a piezo-electriccrystal having at least two pairs of electrodes on opposite sidesthereof, means including phase displacing reactances of differentcharacter directly connecting an electrode of one of said pairs ofelectrodes to the controlling electrodes in said tubes, means directlyconnecting the other electrodes of said pairs of electrodes of saidcrystal to the gridlike anode electrodes in said tubes, a source of.modulating potentials, means for applying modulating potentialsin phaseopposition from said source to said additional grid-like electrodes insaid tubes, and an aperiodic circuit connecting the anodes ofsaid tubesin push-pull relation.

16. In a system-for producing oscillatory energy of I substantiallyconstant frequency and modulating the phase of the said energy inaccordance with signalling potentials, a pair of electron dischargetubes each having a cathode,

\ a plurality of controlling electrodes, and-an output electrode, afrequency stabilizing element, circuits inter-connecting a pair ofcontrolling electrodes in each of said tubes and points on saidfrequency stabilizing element, means for energizing said electrodeswhereby oscillations are produced in.said tubes andcircuits, phaseshifting reactances connected with corresponding controlling electrodesin each of said tubes to produce a relative phase displacement of theoscillations produced by each tube, an output circuit connected with theoutput electrodes of said tubes, a source of modulating potentials andmeans coupling said source of modulating potentials in phase oppositionto like electrodes in said tubes.

17. In a system for producing oscillatoryenergy of substantiallyconstant frequency and modulating the phase of the said energy inaccordance with signalling potentials, a pair of electron dischargetubes each having a cathod aplurality of controlling electrodes, and anout-I /p'ut electrode, a frequency controlling means, circuitsconnecting a pair of. controlling electrodes in each of said tubes tosaid frequency controlling means, means for energizing said electrodeswhereby oscillations are produced in said tubes and circuits, an outputcircuit connectedwith the output electrodes of said tubes 'and' coupledto the oscillation producing electrades and circuits substantially bythe electron stream only of said tubes, means for producing a phasediiference between the oscillation supplied by the respective tubes tosaid output circu t, a source of modulating potentials and meanscoupling said source of modulating potentials in phase opposition tolike electrodes in said tubes.

1 cuits, means for electrostatically shielding the electrodes connectedin said oscillation generating circuits from an electrode connected withsaid output circuit, a source of modulating potentials and means formodulating the phase of the oscillations generatedvin said circuits inaccordance with said modulating-potentials comprising a coupling betweentwo electrodes in said tube and said source of modulating potentials.

GEORGE LINDLEY USSELMAN. 1

